Heretofore, it has been known to alternately laminate a high refractive index layer made of a high refractive index material and a low refractive index layer made of a low refractive index material on a glass substrate to form a glass substrate provided with an optical multilayer film having a function to shut off or transmit light at a specific wavelength. Such a glass substrate provided with an optical multilayer film is used in various fields with its film designed depending upon the purpose of use.
For example, a laminated film comprising a titanium oxide layer as a high refractive index layer and a silicon oxide layer as a low refractive index layer is utilized as an antireflection film having a high visible light transmittance, a low reflectance and a high film resistance. Formation of such an optical multilayer film is usually carried out by a sputtering method, however, a titanium oxide layer formed by a sputtering method has a problem such that cracking may occur by a heat treatment when bending or tempering the glass substrate.
Accordingly, for example, Patent Document 1 discloses a substrate with an antireflection film on which no cracking will occur even when subjected to heat treatment, which comprises a high refractive index layer which is a single layer film (a) of a titanium oxynitride layer, a laminated film (b) containing a titanium oxide layer and a zirconium oxide layer or a laminated film (c) containing a titanium oxynitride layer and a zirconium oxide layer.
Further, for example, Patent Document 2 discloses a glass plate provided with an antireflection film, having an antireflection film on a glass plate, wherein the main component of a material constituting the high refractive index layer in the antireflection film is a metal oxide containing at least one member selected from the group consisting of Co, Al, Si, Zn, Zr and V.